Some aerodynamics problems and some traffic problems

[flag02004]

I created a mission in order to experiment the new Su27 PFM, but i experimented some strange behavior. In my first track, i perform a straight in acceleration, once 1200 kph reached, i pull up to gain almost 80° of climb..... the climb is normal, speed is going down normaly but at almost 8000 feet, the engine RPM fall quickly to 20%, throttle is not responding anymore, the Su27 is going in a flat stall state, falling, upside down.....it happens a second time when joining Mig at medium altitude, i pass them and when i try to speed down using my stick, i entered the same state....

 

In the second track, i was wondering why a lot of aircraft trying to land on an airfield were performing some dive into the ground, without crashing (about 50' after mission start)....and for me, performing an approach, contacting the tower, resquesting "Inbound", then "resquest landing", being authorized to land....landing on the airfield, speed down, authorized to taxi to apron, i went to the communication menu, and i discover that i am still in "inbound", my only option is "abort Inbound"......

Su27PFM_Training.trk

Su27PFM_Training 2.trk

[Robin_Hood]

For the engine spooling down part, make sure you are not applying negative Gs to the aircraft, especially while in afterburner. The fuel reserve for negative-G flight is rather small, and after a short while your engine will shut down from fuel starvation.

 

From what I recall, the manual says something like 3 seconds in afterburner (or 8 seconds above 5 000 m), and 12 ? seconds otherwise (15 seconds above 5 000 m). Not sure about the 12, but something like that.

[SVK_Daniel]

And how to get out from this falling leaf situation?It hapens to me a few times during the flight or fight.It looks like imposible to have dog fight with SU27.If I start dog fights with high manoeuvres,it happens to me always specialy when you lost speed.

[Azrayen]

Best is to not get there. Practice, practice, practice.

If you still get failing leaf, immediately reduce to idle (more time before engines quit) then try to apply thrust and controls to one side only, to "break" the stable inverted stall.

[simo1000rr]

I get this falling leaf situation every time im in the SU to the point i quit already flying the SU , i thought it was something in my game files or something but now seeing that im not the only one and its due to error of me flying the SU maybe i will give it another shot , But question is , Is that how it does in real life ??

[Nedum]

I ask where do the russian pilots train this strange behavior of a Su27 and how to get out of this flat, inverted, stall?

The DCS Su27 is the only modern AC I know, that loves to go inverted, even there is no reason for this behavior.

So it seems that the nose of the DCS Su27 is the thing that gets most effected of a stall, why?

If you look outside at the DCS Su27 during a stall, you can see the nose is stalling, not the whole plane.

The DCS can fall straight to the ground, with no forward momentum and the nose will go up and down.

Why?

I know an old physic law: action = reaction but that doesn't seem to work with the DCS Su27.

 

And the engines blowing out without any negativ Gs.

I was flying with a 45° AoA and full AB, with full forward and up momentum, and the engine blow out!

How could they affected from megatives Gs?

The DCS Su27 is much to agil at low speed at min stick inputs but has nearly no reaction of the stickinput. It's like steering the AC in jelly. A strange behavior for a plane that is famed for his low speed, high AOA agility.

 

I have tried hours of hours to fly this bird as nearly as in a RL Su27 display, but that's impossible. The lack of input reaction and engine power/acceleration at low, high AOA maneuvers makes this impossible for me.

 

It feels all the time wrong to fly with this bird.

I fly the 109, 190, P51, Su25/T, A10C, F15C and I know to land, start and fly this planes, some are very tough but the Su27 is like a AC from another planet. Nothing feels right compared to any other AC in DCS.

Landing is much to easy, but with some strange behaviors (nose stays up till ~140 kph, the only things that get damage are the wheels, and this even at low speeds after a long short breaking). The Su27 has the only engine in DCS that needs to go over 78% power to get after that a reaction beyond 78% power.

And then this ongoing behavior to do a cobra!

I can't believe that the real Su wants to do a Cobra all the time like the DCS Su27 if I pull the stick a little bit to fast (override is off).

The DCS Su27 eats speed/generates drag like no other AC in DCS, because of this strange "Cobra thingie".

 

For me the DCS Su27 is feels wrong in to many ways and even with parctice, practice, practice there is no change to fly an display like in RL.

If someone can do so, please show me a track!

Edited December 24, 2014 by Nedum

[SVK_Daniel]

"I ask where do the russian pilots train this strange behavior of a Su27 and how to get out of this flat, inverted, stall?"Excelent question.

 

I tryed everything even what Azrayen wrote here.I have no luck to get out from that situation and played this simulator since Flaming Clifs.

If it is behavior of real SU 27 ,Russian pilots have to lost nearly each aircraft becouse this model dont allow to get out from this.

 

"A strange behavior for a plane that is famed for his low speed, high AOA agility."

 

Thats absolutelly true.'I cant imagine something like acrobatic low fly with low speed in front of public like SU 27 do it on every show.Not possible with this model I think.

 

Would be nice to see somebody to show track and how to get out of this. :-))

Edited December 24, 2014 by SVK_Daniel

[FSKRipper]

"I ask where do the russian pilots train this strange behavior of a Su27 and how to get out of this flat, inverted, stall?"Excelent question.

 

I tryed everything even what Azrayen wrote here.I have no luck to get out from that situation and played this simulator since Flaming Clifs.

If it is behavior of real SU 27 ,Russian pilots have to lost nearly each aircraft becouse this model dont allow to get out from this.

 

"A strange behavior for a plane that is famed for his low speed, high AOA agility."

 

Thats absolutelly true.'I cant imagine something like acrobatic low fly with low speed in front of public like SU 27 do it on every show.Not possible with this model I think.

 

Would be nice to see somebody to show track and how to get out of this. :-))

 

Please don't judge the flight model by some of your experiences. As I will show with some posts of other users it is possible to fly low speed aerobatics and leave the inverted departure. It's only a matter of training and as a real pilot you can't tell about the abilities of a plane with flying only some minutes or hours.

 

1. Inverted departure (by LQQCN101):

 

discussion: http://forums.eagle.ru/showthread.php?t=134851

 

2. high AOA maneuvers (by Ironhand): http://forums.eagle.ru/showthread.php?t=135959

 

3. Cobra is possible and not scripted. Just fly at low speed (390-400 km/h).

I you insist, I can add a track the next days but you will find a video for sure if you use the search function.

 

4. Don't forget it's still a beta. FM tweaking will continue

 

5. Last but not least and as far as I know, ED is in contact with actual Flanker pilots so I would have some trust in their work.

Edited December 24, 2014 by FSKRipper

[Svend_Dellepude]

Extending the airbrake can help to get out of an inverted stall.

[Ironhand]

...

For me the DCS Su27 is feels wrong in to many ways and even with parctice, practice, practice there is no change to fly an display like in RL.

If someone can do so, please show me a track!

First of all, Merry Christmas to all who celebrate. And best wishes to any who don't.

 

Nedum,

 

I know you take issue with the Flanker's flight model--and not without some reason--but...

 

Just for chuckles, I had some time this morning to play around. I've seen various YouTube videos of various Flanker air show displays and decided to pick the 2013 Radom Su-27 performance. Thought it'd be fun to duplicate it as best I could. While not perfect--I have no idea of what the actual entry/exit altitudes and airspeeds are for each section of the routine--this is a reasonable facsimile. There are two versions of the track. One viewed from inside the cockpit and the other from a fixed spectator's viewpoint. This was recorded with V1.2.14.35513 of the sim.

 

Due to the sim's quirks (or my lack of understanding), in order to view the external (spectator view) track successfully, you'll need to press LAlt+K, if you find yourself looking up through the ground. That should correct it. Also, the changes in zoom I made did't record. So control the zoom with RCtrl+(NumPad)/ and RCtrl+(NumPad)*.

 

Assuming these play back correctly, you should see the sim version of the 2013 Random demonstration as best as I can mimic it without a lot of study. What you will see: 1) double loop immediately after takeoff, 2) a tight level (more or less) turn followed immediately by a climbing left turn, 3) a 2nd climbing turn, 4) an inverted pass (not one of my better efforts), 5) pulling up into another climbing turn, 6) this should have been a loop but I misread my notes and did yet another climbing turn, 7) tailslide, 8 ) a 2nd tailslide, 9) tight turn, 10) slow, high AoA pass, 11) gear down pass and roll), 12) climbing turn into victory roll and, finally, landing.

 

I left taxiing to the parking area and parking the aircraft in the track to show that it's very possible to control taxi speed. I know there are a lot of people taking issue with it.

 

Hope these play back OK. If not, I'll have to find time to convert them and assemble them into a video...which I might do anyway.

 

 

Rich

Edited December 25, 2014 by Ironhand

[bolek]

That is some nice flying!

 

Thanks for sharing

[Ironhand]

That is some nice flying!

 

Thanks for sharing

Thanks. :) Wasn't pushing the envelop too hard, though.

 

LockOn,

 

Especially like those missile launches. :)

 

 

Rich

[Black Cat]

Just wanted to say cheers for the advice in this thread. the Flanker is my first module and posts here have really helped in getting my head around some of the quirks of this aircraft, particularly the negative g characteristics and how to recover from the inverted stall.

 

Great flying from Ironhand and LockOn, has really shown me what this aircraft is capable of... very inspirational :)

[Nedum]

Here's a new one that demonstrates the Su-27 PFM

 

 

I think it handles pretty well after some practice.

 

Thanks, but what you are doing has nothing to do with a RL display I have seen. You are not 10% near.

 

First you use 99% of the time the AB, not nearly realistic.

Second you never flip the Su27 up so the nose falls down (without AB) and accelerate to level flight with a little nose down.

If you try this with the Su27 you will stall.

You can't fly the Su27 any near like a RL display.

I would give up this "Cobra maneuver" for a real good Su27 near RL behavior.

The Corba stalls to easy. she is now the total opposite as to that was I have seen with my own eyes in RL.

I know that this is all beta, but I always hear the ED crew/testers talking that this strange behavior is fine as it is. But this behavior isn't any near the reality.

And I can't understand why so many people in this forum telling the harder a AC is to fly the more near the reality this plane must be.

Myself flew only gliders and my hobby is RC flying (Jets and Helis), but I never saw and felt such a strange behavior like at this plane (DCS Su27).

This AC is completely different to all other Planes from DCS and from that I have seen/ I know.

 

So as I said before. Anyone show me a display (as track) flown like in RL and I will never ever say this FM is wrong, but till this day I will not believe that this FM is any near the reality!

[Ironhand]

...

 

So as I said before. Anyone show me a display (as track) flown like in RL and I will never ever say this FM is wrong, but till this day I will not believe that this FM is any near the reality!

I think you might have missed the links in my earlier post above: DCS Su-27 at 2013 Radom. Tracks are at the bottom of the post. (They were made with the previous version of the sim but played back correctly with the last update a few days ago.)

 

I enjoy watching the 2013 Radom routine (YouTube) where there are several videos of it taken from different angles. So that was the one I decided to try to reproduce. Certainly not perfect but I don't have many hours in the aircraft nor, unfortunately, can I afford the time to perfect the routine. :) But, when I compare it to what I see in the videos, I think it's a reasonable facsimile.

 

While there are regions in the flight model that don't "feel" right, there are definitely areas that "feel" correct. Anyway, I'll be interested in hearing your thoughts after viewing the tracks and/or video.

 

 

Rich

Edited December 30, 2014 by Ironhand

[Ironhand]

...

Second you never flip the Su27 up so the nose falls down (without AB) and accelerate to level flight with a little nose down.

If you try this with the Su27 you will stall.

Is this more like what you are looking for? The track is attached. Haven't spent much time trying to perfect it but there's never any need to jam the throttle into afterburner.

 

Edit: This track was made with V1.2.14.35605.

Edited December 31, 2014 by Ironhand

[amazingme]

You're right..

 

I ask where do the russian pilots train this strange behavior of a Su27 and how to get out of this flat, inverted, stall?

The DCS Su27 is the only modern AC I know, that loves to go inverted, even there is no reason for this behavior.

So it seems that the nose of the DCS Su27 is the thing that gets most effected of a stall, why?

If you look outside at the DCS Su27 during a stall, you can see the nose is stalling, not the whole plane.

The DCS can fall straight to the ground, with no forward momentum and the nose will go up and down.

Why?

I know an old physic law: action = reaction but that doesn't seem to work with the DCS Su27.

 

And the engines blowing out without any negativ Gs.

I was flying with a 45° AoA and full AB, with full forward and up momentum, and the engine blow out!

How could they affected from megatives Gs?

The DCS Su27 is much to agil at low speed at min stick inputs but has nearly no reaction of the stickinput. It's like steering the AC in jelly. A strange behavior for a plane that is famed for his low speed, high AOA agility.

 

I have tried hours of hours to fly this bird as nearly as in a RL Su27 display, but that's impossible. The lack of input reaction and engine power/acceleration at low, high AOA maneuvers makes this impossible for me.

 

It feels all the time wrong to fly with this bird.

I fly the 109, 190, P51, Su25/T, A10C, F15C and I know to land, start and fly this planes, some are very tough but the Su27 is like a AC from another planet. Nothing feels right compared to any other AC in DCS.

Landing is much to easy, but with some strange behaviors (nose stays up till ~140 kph, the only things that get damage are the wheels, and this even at low speeds after a long short breaking). The Su27 has the only engine in DCS that needs to go over 78% power to get after that a reaction beyond 78% power.

And then this ongoing behavior to do a cobra!

I can't believe that the real Su wants to do a Cobra all the time like the DCS Su27 if I pull the stick a little bit to fast (override is off).

The DCS Su27 eats speed/generates drag like no other AC in DCS, because of this strange "Cobra thingie".

 

For me the DCS Su27 is feels wrong in to many ways and even with parctice, practice, practice there is no change to fly an display like in RL.

If someone can do so, please show me a track!

 

 

I have the exactly same frustrations related to the "new" Flanker.. It's not what it used to be.. and it doesn't match what it IS believed in real life: "Russian emphasis on close-range slow-speed supermaneuverability runs counter to Western Energy–maneuvrability theory, which favors retaining kinetic energy to control the range of the engagement."

 

I don't see the maneuvrability anymore.. Su27... R.I.P :(

[amazingme]

Exactly

 

Thanks, but what you are doing has nothing to do with a RL display I have seen. You are not 10% near.

 

First you use 99% of the time the AB, not nearly realistic.

Second you never flip the Su27 up so the nose falls down (without AB) and accelerate to level flight with a little nose down.

If you try this with the Su27 you will stall.

You can't fly the Su27 any near like a RL display.

I would give up this "Cobra maneuver" for a real good Su27 near RL behavior.

The Corba stalls to easy. she is now the total opposite as to that was I have seen with my own eyes in RL.

I know that this is all beta, but I always hear the ED crew/testers talking that this strange behavior is fine as it is. But this behavior isn't any near the reality.

And I can't understand why so many people in this forum telling the harder a AC is to fly the more near the reality this plane must be.

Myself flew only gliders and my hobby is RC flying (Jets and Helis), but I never saw and felt such a strange behavior like at this plane (DCS Su27).

This AC is completely different to all other Planes from DCS and from that I have seen/ I know.

 

So as I said before. Anyone show me a display (as track) flown like in RL and I will never ever say this FM is wrong, but till this day I will not believe that this FM is any near the reality!

 

I have the same feeling now about the Flanker. I hope ED will come to their senses and... make it instead of break it.

[FSKRipper]

I have the same feeling now about the Flanker. I hope ED will come to their senses and... make it instead of break it.

 

As seen above, Ironhand posted tracks flown with the Su-27 AFM mimicking a real flight program. Thats all you and Nedum asked for. But sure that's nothing against your feelings :thumbup:

[flymasta]

i've read here that the su-27 inverted stall problem, is because we need to learn how to fly this model, that it's not a BUG.

i couldn't disagree more

1st i have FC3 up to date i've flown the su-27 and su-33 and they handle more or less the same

i purchased FC3 back in NOV. and flown the su-27 pushed it to the limit and then some and never got the model to stall like this.

now after the recent update is when i notice the problem and so far it only happen in the GAUNTLET MISSION i have not flown all the su-27 mission but non the less the ONLY MISSION that the INVERTED STALL HAPPENS IS THE "GAUNTLET MISSION".

i don't even have to try anything difficult a simple bank right or left and i loose control .

again this don't happen in any of the other SU-27 MISSIONS i've tried so far!

Also you have to trim the hell out of it to get it level this wasn't the case before the latest update

thank you in advance for any help anyone can provide

[Esac_mirmidon]

Try open the mission with the editor and resave it again.

[FSKRipper]

If it don't work post a track please. No track = it didn't happen.

 

BTW @amazingme, Azrayen has posted a track in the inverted departure threat which is an answer for your demand. He flies the Cobra with 300km/h IAS.

Edited January 7, 2015 by FSKRipper